Manganese dioxide is known and widely used as a solid electrolyte in electrolyte capacitors. Such capacitors are conventionally formed by first anodizing a valve-metal anode (e.g., tantalum) to form a dielectric oxide coating, and thereafter immersing the oxide-coated anode in an aqueous solution of manganese nitrate. After a sufficient period of time, the wet anode is heated to cause pyrolytic decomposition of the manganese nitrate to manganese dioxide. The capacitor element is also typically coated with graphite and silver layers, and then encapsulated with a resin. Unfortunately, one problem with conventional manganese oxide capacitors is that the encapsulating resin (e.g., epoxy resin) is often unstable in extreme environments, i.e., high temperature (e.g., above about 175° C.) and/or high voltage (e.g., above about 35 volts). Attempts to remove the resin, however, can adversely impact electrical performance by allowing moisture to contact the capacitor element.
As such, a need currently exists for a solid electrolytic capacitor having improved performance in high temperature and/or high voltage environments.